While folding and tucking apparati have long been known and used on forming, filling and sealing machines for liquid products, such as milk and juices, heretofore such apparati have typically included oppositely pivotable arms or blades which rub along a heat-activated, plastic coated panel surface, tending to scuff or mar such printed or colored surface. Typical of such blades are those shown and described in U.S. Pat. No. 3,398,659.